Tensile stress resistant multilayer ceramic capacitor

ABSTRACT

A multilayer ceramic capacitor is configured such that “a” is a distance in a height direction between an effective portion and a first principal surface; “b” is a distance in a length direction between a first end surface and the effective portion in the length direction; “c” is a thickness of the thickest portion of a first base layer provided over the first principal surface; “d” is a distance in the length direction between the thickest portion of the first base layer provided over the first end surface and a portion of the first base layer located over the first principal surface and closest to a second end surface; and “e” is a maximum thickness of a portion of the first base layer provided over the first end surface; and f: the height of the ceramic body, and 2≦(c·d+e·f/2)/(a·b)≦6 is satisfied.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a multilayer ceramic capacitor.

2. Description of the Related Art

In recent years, with the reduction in size and height of electronicdevices such as cellular phones and portable music players, wiringboards mounted on the electronic devices have been progressively reducedin size. Accordingly, multilayer ceramic capacitors mounted on thewiring boards have been also progressively reduced in size and height.

As a method for densely arranging multilayer ceramic capacitors on thewiring boards, for example, it is conceivable that multilayer ceramiccapacitors are built into multilayer printed wiring boards (for example,see Japanese Patent Application Laid-Open No. 2002-203735).

The multilayer ceramic capacitors built in multilayer printed wiringboards as described in Japanese Patent Application Laid-Open No.2002-203735 are required to be thin. However, the mechanical strength ofthe multilayer ceramic capacitors tends to decrease as the multilayerceramic capacitors are reduced in height. Additionally, in the case offorming external electrodes from a conductive paste, the conductivepaste is applied to ends of ceramic bodies, and baked, and in this case,the contraction force (tensile stress) of the conductive paste itself isalso applied to the ceramic bodies. Then, this stress remains asresidual stress in the multilayer ceramic capacitors, thus furtherdecreasing the mechanical strength of the multilayer ceramic capacitors.Accordingly, the multilayer ceramic capacitors are more likely to becracked. In particular, thin multilayer ceramic capacitors are likely tohave residual stress caused at ridges of ceramic bodies. For thisreason, the thin multilayer ceramic capacitors are likely to be crackedfrom the ridges of the ceramic bodies into the ceramic bodies.

The residual stress in the case of firing is likely to increase as theceramic bodies are reduced in height, and increase as the externalelectrodes are increased in volume.

SUMMARY OF THE INVENTION

Preferred embodiments of the present invention provide a multilayerceramic capacitor which is unlikely to be cracked from ridges of aceramic body into the ceramic body.

A multilayer ceramic capacitor according to a preferred embodiment ofthe present invention includes a ceramic body, a first internalelectrode, a second internal electrode, a first external electrode, anda second external electrode. The ceramic body includes first and secondprincipal surfaces, first and second side surfaces, and first and secondend surfaces. The first and second principal surfaces extend in thelength direction and width direction. The first and second side surfacesextend in the length direction and height direction. The first andsecond end surfaces extend in the width direction and the heightdirection. The first internal electrode extends in the length directionand width direction in the ceramic body. The first internal electrodeextends to the first end surface. The second internal electrode extendsin the length direction and width direction in the ceramic body, and isopposed in the height direction to the first internal electrode with aceramic portion interposed therebetween. The second internal electrodeextends to the second end surface. The first external electrode isconnected to the first internal electrode. The first external electrodeis provided over the first end surface, and over each of the first andsecond principal surfaces. The second external electrode is connected tothe second internal electrode. The second external electrode is providedover the second end surface, and over each of the first and secondprincipal surfaces. The first external electrode includes a first baselayer provided over the ceramic body and including a metal and glass,and a first plated layer provided over the first base layer. The secondexternal electrode includes a second base layer provided over theceramic body and including a metal and glass, and a second plated layerprovided over the second base layer.

In a preferred embodiment of the present invention, “a” is a distance inthe height direction between the first principal surface and an end inthe length direction of an effective portion that refers to a regionwhere the first internal electrode and the second internal electrode areopposed in the height direction; “b” is a distance in the lengthdirection between the first end surface and the effective portion in thelength direction; “c” is a maximum thickness of a portion of the firstbase layer provided over the first principal surface; “d” is a distancein the length direction between a point of the first base layer over thefirst end surface which is farthest from the first end surface and anend of the first base layer over the first principal surface which isclosest to the second end surface; “e” is a maximum thickness of aportion of the first base layer provided over the first end surface; and“f” is a height of the ceramic body, and a condition2≦(c·d+e·f/2)/(a·b)≦6 is satisfied.

A multilayer ceramic capacitor according to a preferred embodiment ofthe present invention is preferably about 0.9 mm to about 1.1 mm inlength dimension, about 0.4 mm to about 0.6 mm in width dimension, andabout 0.085 mm to about 0.15 mm in height dimension.

In a multilayer ceramic capacitor according to a preferred embodiment ofthe present invention, the first and second plated layers eachpreferably include a Cu plated layer.

According to various preferred embodiments of the present invention, amultilayer ceramic capacitor that is unlikely to be cracked from ridgesof a ceramic body into the ceramic body is provided.

The above and other elements, features, steps, characteristics andadvantages of the present invention will become more apparent from thefollowing detailed description of the preferred embodiments withreference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic perspective view of a multilayer ceramic capacitoraccording to a preferred embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view of FIG. 1 along the lineII-II.

FIG. 3 is a schematic side view of a multilayer ceramic capacitoraccording to a preferred embodiment of the present invention.

FIG. 4 is a schematic cross-sectional view of a multilayer ceramiccapacitor according to a modification example of a preferred embodimentof the present invention.

FIG. 5 is a schematic cross-sectional view of a portion of a multilayerceramic capacitor according to a modification example of a preferredembodiment of the present invention.

FIG. 6 is a schematic cross-sectional view of a portion of a multilayerceramic capacitor according to a modification example of a preferredembodiment of the present invention.

FIG. 7 is a schematic cross-sectional view of a multilayer ceramiccapacitor according to a modification example of a preferred embodimentof the present invention.

FIG. 8 is a schematic cross-sectional view of a multilayer ceramiccapacitor according to a modification example of a preferred embodimentof the present invention.

FIG. 9 is a schematic cross-sectional view of a multilayer ceramiccapacitor according to a modification example of a preferred embodimentof the present invention.

FIG. 10 is a schematic cross-sectional view of a multilayer ceramiccapacitor according to a modification example of a preferred embodimentof the present invention.

FIG. 11 is a schematic cross-sectional view of a multilayer ceramiccapacitor according to a modification example of a preferred embodimentof the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of the present invention will be described belowwith reference to examples. However, the following preferred embodimentswill be provided merely by way of example. The present invention is notlimited to the following preferred embodiments in any way.

In addition, members that have the same or substantially the samefunctions shall be denoted by the same reference symbols in therespective drawings referenced in the preferred embodiments, etc. Inaddition, the drawings referenced in the preferred embodiments, etc. areschematically made. The dimensional ratios or the like between theobjects drawn in the drawings may differ from the dimensional ratios orthe like between real objects. The dimensional ratios or the likebetween the objects may also differ between the drawings. The specificdimensional ratios or the like of the objects should be determined inview of the following description.

As shown in FIGS. 1 through 3, a multilayer ceramic capacitor 1 includesa ceramic body 10. The ceramic body 10 can be formed from, for example,a dielectric ceramic material. Specific examples of the dielectricceramic material include, for example, BaTiO₃, CaTiO₃, SrTiO₃, andCaZrO₃. With the above ceramic material as a main constituent, accessoryconstituents such as, for example, Mn compounds, Mg compounds, Sicompounds, Fe compounds, Cr compounds, Co compounds, Ni compounds, andrare-earth compounds may be added appropriately to the ceramic body 10,depending on desired characteristics of the multilayer ceramic capacitor1.

In the present preferred embodiment, the ceramic body 10 preferably hasa cuboid shape. The “cuboid shape” herein is considered to encompasscuboids with corners or ridges rounded.

The ceramic body 10 includes first and second principal surfaces 10 a,10 b, first and second side surfaces 10 c, 10 d, and first and secondend surfaces 10 e, 10 f. The first and second principal surfaces 10 a,10 b each extend in the length direction L and the width direction W.The first and second side surfaces 10 c, 10 d each extend in the lengthdirection L and the height direction T. The first and second endsurfaces 10 e, 10 f each extend in the width direction W and the heightdirection T.

The multilayer ceramic capacitor 1 is preferably about 0.9 mm to about1.1 mm in length dimension. The multilayer ceramic capacitor 1 ispreferably about 0.4 mm to about 0.6 mm in width dimension. Themultilayer ceramic capacitor 1 is preferably about 0.085 mm to about0.15 mm in height dimension. When the height dimension, lengthdimension, and width dimension of the ceramic body 10 are referred torespectively as DT, DL, and DW, the condition of DT<DW<DL, (1/7)DW≦DT≦(¼)DW, or DT<about 0.15 mm is preferably met.

As shown in FIG. 2, pluralities of first and second internal electrodes11, 12 that are substantially rectangular are disposed within theceramic body 10. The first and second internal electrodes 11, 12 eachextend in the length direction L and the width direction W. The firstinternal electrodes 11 are extended to the first end surface 10 e, butnot exposed to the second end surface 10 f or the first and second sidesurfaces 10 c, 10 d. On the other hand, the second internal electrodes12 are extended to the second end surface 10 f, but not exposed to thefirst end surface 10 e or the first and second side surfaces 10 c, 10 d.The first internal electrodes 11 and the second internal electrodes 12are alternately provided at intervals mutually in the height directionT. The ceramic portions 10 g provided between the first internalelectrodes 11 and the second internal electrodes 12 can be adjusted to,for example, on the order of about 0.5 μm to about 10 μm in height. Thefirst and second internal electrodes 11, 12 can be adjusted to, forexample, on the order of about 0.2 μm to about 2 μm in height.

The first and second internal electrodes 11, 12 can be composed of anappropriate conductive material. The first and second internalelectrodes 11, 12 can be composed of, for example, a metal such as Ni,Cu, Ag, Pd, and Au, or an alloy containing one of the metals, such as,for example, an Ag—Pd alloy.

A glass layer may be formed on exposed portions of the internalelectrodes at the end surfaces 10 e, 10 f. The formation of the glasslayer on the exposed portions of the internal electrodes 11, 12 ensuresresistance to moisture and plating even when the external electrodes 13,14 are insufficiently dense, significantly reduces or prevents ingressof moisture from the outside into the ceramic body 10, and improvesresistance to moisture and plating.

The first and second external electrodes 13, 14 are provided over theceramic body 10.

The first external electrode 13 is connected to the first internalelectrodes 11. The first external electrode 13 is provided incommunication with the first end surface 10 e, and each of the first andsecond principal surfaces 10 a, 10 b as well as the first and secondside surfaces 10 c, 10 d. It is to be noted that the first externalelectrode may be provided in communication with only the first endsurface and at least one of the first and second principal surfaces in apreferred embodiment of the present invention.

The second external electrode 14 is connected to the second internalelectrodes 12. The second external electrode 14 is provided incommunication with the second end surface 10 f, and each of the firstand second principal surfaces 10 a, 10 b as well as the first and secondside surfaces 10 c, 10 d. It is to be noted that the second externalelectrode may be provided in communication with only the second endsurface and at least one of the first and second principal surfaces in apreferred embodiment of the present invention.

The first external electrode 13 includes a first base layer 13 a and afirst Cu plated layer 13 b. The first base layer 13 a is provided overthe ceramic body 10. The first base layer 13 a can be formed by firing aconductive paste layer formed by applying a conductive paste, forexample.

The first base layer 13 a includes a metal and glass. Examples of themetal included in the first base layer 13 a include, for example,appropriate metals such as Ni, Cu, Ag, Pd, Au, and Ag—Pd alloys.

The first base layer 13 a is preferably about 1 μm to about 20 μm inthickness.

The first plated layer 13 b is provided over the first base layer 13 a.The first plated layer can be composed of, for example, Cu, Ni, Ag, Pd,an Ag—Pd alloy, Au, or Sn. It is to be noted that the first plated layer13 b may be formed from a laminate body of multiple plated layers. Thefirst plated layer 13 b configured to have two-layer structure of, forexample, Ni plating and Sn plating also makes it possible to mount themultilayer ceramic capacitor on the surface of a multilayer printedwiring board, rather than as a multilayer ceramic capacitor built in amultilayer printed wiring board. In the case of using the capacitorbuilt in a multilayer printed wiring board, the first plated layer 13 bis preferably Cu. As just described, when the outermost layer of theexternal electrode 13 includes a Cu plated film, it becomes possible touse the multilayer ceramic capacitor 1 as an electronic component builtin a multilayer printed wiring board.

In addition, in the case of embedding the multilayer ceramic capacitor 1into a multilayer printed wiring board, there is a need to provide a viahole for electronic component connection in the multilayer printedwiring board, in order to provide electrical connection to the firstexternal electrode 13. This via hole for electronic component connectionis formed with the use of a laser such as a CO₂ laser, for example. Inthe case of forming the via hole with the use of a laser, the firstexternal electrode 13 of the multilayer ceramic capacitor 1 is directlyirradiated with the laser. In this case, when the first plated layer 13b of the first external electrode 13 includes a Cu plated layer, thelaser can be reflected at a high reflectance, and the capacitor is thusable to be used in a preferred manner as the multilayer ceramiccapacitor 1 to be embedded into a multilayer printed wiring board. Whenthe laser reflectance is low with respect to the first externalelectrode 13 of the multilayer ceramic capacitor 1, the laser may reacheven the inside of the multilayer ceramic capacitor 1, and damage themultilayer ceramic capacitor 1.

In addition, the surface of the first plated layer 13 b may be at leastpartially oxidized. For example, the first plated layer 13 b preferablyhas ridges oxidized. In this case, when the multilayer ceramic capacitor1 is embedded into a wiring board, the oxidized portions and resin ofthe wiring board are attached through oxygen binding, and the adhesionstrength between the first external electrode 13 and the resin wiringboard is thus increased. It is to be noted that the effect mentionedabove is greater when the entire surface of the first external electrode13 is oxidized.

The first Cu plated layer 13 b is preferably about 1 μm to about 10 μmin thickness.

The second external electrode 14 includes a second base layer 14 a and asecond Cu plated layer 14 b. The second base layer 14 a is provided overthe ceramic body 10. The second base layer 14 a can be formed by firinga conductive paste layer formed by applying a conductive paste, forexample.

The second base layer 14 a includes a metal and glass. Examples of themetal included in the second base layer 14 a include, for example,appropriate metals such as Ni, Cu, Ag, Pd, Au, and Ag—Pd alloys.

The second base layer 14 a is preferably about 1 μm to about 20 μm inthickness.

The second Cu plated layer 14 b is provided over the second base layer14 a. The surface of the second Cu plated layer 14 b may be at leastpartially oxidized. For example, the second Cu plated layer 14 bpreferably has ridges oxidized. In this case, when the capacitor isembedded into a wiring board, the oxidized portions and resin of thewiring board are attached through oxygen binding, and the adhesionstrength between the second external electrode 14 and the resin wiringboard is thus able to be increased. It is to be noted that the effectmentioned above is greater when the entire surface of the secondexternal electrode 14 is oxidized.

The second Cu plated layer 14 b is preferably about 1 μm to about 10 μmin thickness.

It is to be noted that the second Cu plated layer 14 b may includemultiple layers instead of just one layer.

As just described, when the outermost layer of the second externalelectrode 14 includes a Cu plated film, it becomes possible to use themultilayer ceramic capacitor 1 as an electronic component built in amultilayer printed wiring board.

In addition, in the case of embedding the multilayer ceramic capacitor 1into a multilayer printed wiring board, there is a need to provide a viahole for electronic component connection in the multilayer printedwiring board, in order to provide electrical connection to the secondexternal electrode 14. This via hole for electronic component connectionis formed with the use of a laser such as a CO₂ laser, for example. Inthe case of forming the via hole with the use of a laser, the secondexternal electrode 14 of the multilayer ceramic capacitor 1 is directlyirradiated with the laser. In this case, when the second plated layer 14b of the second external electrode 14 includes a Cu plated layer, thelaser can be reflected at a high reflectance, and the capacitor is thusable to be used in a preferred manner as the multilayer ceramiccapacitor 1 to be embedded into a multilayer printed wiring board. Whenthe laser reflectance is low with respect to the second externalelectrode of the multilayer ceramic capacitor 1, the laser may reacheven the inside of the multilayer ceramic capacitor 1, and damage themultilayer ceramic capacitor 1.

As described above, the first and second base layers 13 a, 14 a can beformed by, for example, a dip method. Specifically, the layers can beformed in such a way that ends of the ceramic body 10 are immersed in aconductive paste, dried, and then baked. When the first and second baselayers 13 a, 14 a are prepared by such a preparation method, the firstand second external electrodes 13, 14 are typically not uniform inthickness. For example, the thicknesses of portions located over thefirst principal surface 10 a for each of the first and second externalelectrodes 13, 14 are gradually increased once, and gradually decreasedoutward from the center of the ceramic body 10 in the length directionL.

The metal in the internal electrodes 11, 12 is preferably diffused inthe external electrodes 13, 14. The diffusion of the metal in theinternal electrodes 11, 12 to the external electrodes 13, 14 expands thevolume of the metal in the external electrodes 13, 14 to fill minutegaps in the external electrodes 13, 14, thus improving the sealingproperty against ingress of moisture. It is to be noted that thediffusion distance of the metal in the internal electrodes 11, 12 to theexternal electrodes 13, 14 is preferably about 4 μm or more.

It is to be noted that the first and second external electrodes 13, 14may be each at least partially embedded in the first and secondprincipal surfaces 10 a, 10 b.

The terminal sides of portions of the first and second externalelectrodes 13, 14 located over the first and second principal surfaces10 a, 10 b may be linear, convex, or concave, but preferably morelinear. The linear shape herein refers to, when the line connecting bothends at end edges of the first external electrode 13 and second externalelectrode 14 located on the principal surfaces 10 a, 10 b is regarded asa reference line P in planar view, a shape where the width h withrespect to the reference line P is not more than about ±30 μm away fromthe positions of the centers in the width direction (the positions atabout ½ dimension in the width direction) of the end edges of the firstexternal electrode 13 and second external electrode 14. When theportions of the first and second external electrodes 13, 14 located overthe first and second principal surfaces 10 a, 10 b have linear endsides, the first external electrode 13 and the second external electrode14 can be formed uniformly even at both ends of the ceramic body 10 inthe width direction. As a result, even when the laser for irradiation issomewhat shifted in embedding the multilayer ceramic capacitor 1 into amultilayer printed wiring board, it is possible to irradiate thesurfaces of the first external electrode 13 and second externalelectrode 14 with the laser, and the probability of joint is increasedbetween the via hole and the multilayer ceramic capacitor 1.

A method for manufacturing the multilayer ceramic capacitor 1 is notparticularly limited. The multilayer ceramic capacitor 1 can bemanufactured, for example, in the following manner.

First, ceramic green sheets are prepared to define the ceramic body 10.Next, conductive paste layers are formed by applying a conductive pasteonto the ceramic green sheets. The conductive paste can be applied byvarious printing methods such as a screen printing method, for example.The conductive paste may contain a binder and a solvent besidesconductive particulates.

Next, a plurality of ceramic green sheets without any conductive pastelayer formed, the ceramic green sheets with conductive paste layersformed to correspond to the first or second internal electrodes, and aplurality of ceramic green sheets without any conductive paste layerprovided thereon are stacked in this order, and pressed in the stackingdirection to prepare a mother laminate body.

Next, the mother laminate body is cut along a virtual cut line on themother laminate body to prepare a plurality of raw ceramic laminatebodies from the mother laminate body. It is to be noted that the motherlaminate body can be cut with a dicing machine or a pushing machine. Theraw ceramic laminate bodies may be subjected to barrel polishing or thelike to have ridges or corners rounded.

Next, the raw ceramic laminate bodies are subjected to firing. In thisfiring step, the first and second internal electrodes are fired. Thefiring temperature can be set appropriately depending on the types ofthe ceramic material and conductive paste used. The firing temperaturecan be adjusted to, for example, on the order of about 900° C. to about1300° C.

Next, a conductive paste is applied by a method such as dipping to bothends of the fired ceramic laminate bodies (ceramic bodies). Next, theconductive paste applied to the ceramic laminate body is subjected tohot-air drying for about 10 minutes at about 60° C. to about 180° C.,for example. Thereafter, the dried conductive paste is baked to formbase layers. The baking temperature is preferably adjusted to, forexample, about 780° C. to about 900° C.

It is to be noted that with the conductive paste layers formed inadvance on the raw ceramic body, the base layers may be subjected toco-firing with the ceramic body and the internal electrodes.

Thereafter, the multilayer ceramic capacitor 1 can be completed byforming one or more plated layers on the base layers.

Now, in firing the raw ceramic body with the conductive paste layersformed to define the first and second base layers 13 a, 14 a, theconductive paste layers contract more than the raw ceramic body. Forthis reason, tensile stress is applied to ridges of the ceramic body 10by contraction of portions of the conductive paste layers located on theprincipal surfaces, and contraction of portions of the conductive pastelayers located on the end surfaces. This tensile stress makes crackslikely to be generated from the ridges of the ceramic body 10.

As shown in FIG. 2, “a” is a distance in the height direction between aneffective portion E that refers to a region where the first internalelectrodes 11 and the second internal electrodes 12 are opposed in theheight direction T, and the first principal surface 10 a; “b” is adistance in the length direction between the first end surface 10 e andthe effective portion E in the length direction L; “c” is a maximumthickness of a portion of the first base layer 13 a provided over thefirst principal surface 10 a; “d” is a distance in the length directionL between the thickest portion of the first base layer 13 a providedover the first end surface 10 e and a portion of the first base layer 13a closest to the second end surface 10 f, which is located over thefirst principal surface 10 a; “e” is a maximum thickness of a portion ofthe first base layer 13 a provided over the first end surface 10 e; and“f” is a height of the ceramic body 10.

In the multilayer ceramic capacitor 1, the ratio (c·d+e·f/2)/(a·b) ispreferably 6 or less. For this reason, with the large (a·b), the ridgesof the ceramic body 10 undergo an increase in strength. In addition, thetensile stress applied to the ridges of the ceramic body 10 is reducedbecause the first base layer 13 a is thin with the small (c·d+e·f/2).Therefore, the multilayer ceramic capacitor 1 is unlikely to be crackedfrom the ridges of the ceramic body 10.

Furthermore, the ratio (c·d+e·f/2)/(a·b) is preferably or more. For thisreason, the first base layer 13 a is not excessively thin. Accordingly,the multilayer ceramic capacitor 1 has excellent resistance to moisture.

It is to be noted that the thicknesses of the base layers 13 a, 14 a canbe measured by observing, with a microscope, a cross section exposed bypolishing the first or second side surface 10 c, 10 d of the multilayerceramic capacitor 1 until the height of the multilayer ceramic capacitor1 is reduced to about ½.

The distance a in the height direction between an effective portion Ewhere the first internal electrodes 11 and the second internalelectrodes 12 are opposed in the height direction T and the firstprincipal surface 10 a can be measured by observing, with a microscope,a cross section exposed by polishing the first or second side surface 10c, 10 d of the multilayer ceramic capacitor 1 until the height of themultilayer ceramic capacitor 1 is reduced to about ½.

In the length direction L, the distance b in the length directionbetween the first end surface 10 e and the effective portion E isreferred to as the distance between the internal electrode 12 extendingclosest to the first end surface 10 e among the second internalelectrodes 12 and the first end surface 10 e in a cross section exposedby polishing the first or second side surface 10 c, 10 d of themultilayer ceramic capacitor 1 until the height of the multilayerceramic capacitor 1 is reduced to about ½.

The height f of the ceramic body 10 can be obtained by measuring theheight of the center in the width direction W in a cross sectionobtained by polishing the first or second end surface of the ceramicbody 10 until the height of the ceramic body 10 in the length directionL is reduced to about ½.

It is to be noted that the distance a in the height direction betweenthe effective portion E where the first internal electrodes 11 and thesecond internal electrodes 12 are opposed in the height direction T andthe first principal surface 10 a can be varied by, in stacking greensheets, increasing or decreasing the number of green sheets stackedwithout forming any conductive paste layer.

In the length direction L, the distance b in the length directionbetween the first end surface 10 e and the effective portion E can becontrolled by varying the size of the electrode figure of a printingplate used to form the conductive paste layers onto the green sheets.

The height f of the ceramic body 10 can be varied arbitrarily dependingon the combination of the height of the green sheets with conductivepaste layers formed, that is, the effective layers, with the outer layerheight.

The thickness c of a portion of the first base layer 13 a provided overthe first principal surface 10 a is able to be adjusted depending on thecombination of the viscosity of a paste in which the ceramic body isimmersed by a dip process, the thickness of the paste layer, the pull-uprate after the immersion of the ceramic body, etc.

The distance d in the length direction L between the thickest portion ofthe first base layer 13 a provided over the first end surface 10 e and aportion of the first base layer 13 a closest to the second end surface10 f, which is located over the first principal surface 10 a is able tobe adjusted depending on the combination of the viscosity of a paste inwhich the ceramic body is immersed by a dip process, the paste thicknessin the paste bath, the period of time for which the ceramic body isimmersed in the paste, etc.

The thickness e of a portion of the first base layer 13 a provided overthe first end surface 10 e is able to be adjusted depending on thecombination of the viscosity of a paste in which the ceramic body isimmersed by a dip process, the thickness of the paste layer, the pull-uprate after the immersion of the ceramic body, etc. In addition,depending on the condition for the pull-up, it is possible to change themagnitude relationship with the thickness of the portion of the firstbase 13 a provided over the first principal surface 10 a.

The height f of the ceramic body 10 can be varied arbitrarily dependingon the combination of the height of the green sheets with conductivepaste layers formed, that is, the effective layers, with the outer layerheight.

Now, for example, in a case of forming an external electrode by firingconductive paste layers formed by a dip method or the like, a portion ofthe external electrode located on the first principal surface may bedifferent in length from a portion thereof located on the secondprincipal surface. In such a case, the position in the length directionof the thickest portion of the external electrode located on the firstprincipal surface is different from the position in the length directionof the thickest portion thereof located on the second principal surface.Mounting this multilayer ceramic capacitor on a mounting substrate withthe use of a mounter increases the possibility that the multilayerceramic capacitor is cracked.

In this regard, as shown in FIG. 7, the length of the first externalelectrode 13 in the length direction L is referred to as LE1 as viewedfrom the second principal surface 10 b. The length of the first externalelectrode 13 in the length direction L is referred to as LE2 as viewedfrom the first principal surface 10 a. The length of the second externalelectrode 14 in the length direction L is referred to as LE3 as viewedfrom the second principal surface 10 b. The length of the secondexternal electrode 14 in the length direction L is referred to as LE4 asviewed from the first principal surface 10 a. The distance in the lengthdirection L is referred to as LE5 between the thickest portion of thefirst external electrode 13 located on the second principal surface 10 band the outermost end of the first external electrode 13 in the lengthdirection L. The distance in the length direction L is referred to asLE6 between the thickest portion of the first external electrode 13located on the first principal surface 10 a and the outermost end of thefirst external electrode 13 in the length direction L. The distance inthe length direction L is referred to as LE7 between the thickestportion of the second external electrode 14 located on the secondprincipal surface 10 b and the outermost end of the second externalelectrode 14 in the length direction L. The distance in the lengthdirection L is referred to as LE8 between the thickest portion of thesecond external electrode 14 located on the first principal surface 10 aand the outermost end of the second external electrode 14 in the lengthdirection L. The ratio of the absolute value of the difference betweenLE5 and LE6 to the longer one of LE1 and LE2 ((absolute value ofdifference between LE5 and LE6)/(longer one of LE1 and LE2)) is referredto as A1. The ratio of the absolute value of the difference between LE7and LE8 to the longer one of LE3 and LE4 ((absolute value of differencebetween LE7 and LE8)/(longer one of LE3 and LE4)) is referred to as A2.

In the multilayer ceramic capacitor 1, A1 and A2 are each about 0.2 orless. For this reason, as can be also seen from the results of thefollowing experimental examples, the ceramic body 10 is unlikely to becracked in mounting the multilayer ceramic capacitor 1 on a mountingsubstrate with the use of a mounter.

Further, in regard to LE1 and LE3, a cross section is exposed bypolishing the first or second side surface 10 c, 10 d of the multilayerceramic capacitor 1 until the dimension in the width direction W isreduced down to about ½. The dimensions can be obtained by observing thecross section of the multilayer ceramic capacitor from the secondprincipal surface with the use of an optical microscope, and measuringthe length of the external electrode in the center in the widthdirection W

In regard to LE2 and LE4, a cross section is exposed by polishing thefirst or second side surface 10 c, 10 d of the multilayer ceramiccapacitor 1 until the dimension in the width direction W is reduced downto about ½. The dimensions can be obtained by observing the crosssection of the multilayer ceramic capacitor from the first principalsurface with the use of an optical microscope, and measuring the lengthof the external electrode in the center in the width direction W.

In regard to LE5 to LE8, a cross section is exposed by polishing theside surface of the multilayer ceramic capacitor until the dimension inthe width direction W is reduced down to about ½. This cross section isobserved with the use of an optical microscope to specify the thickestportion of the external electrode located on the principal surface.Next, the dimensions can be obtained by measuring the distance betweenthe thickest portion and the outermost end of the external electrode.

The length in the length direction of the portion of the externalelectrode located on the principal surface can be controlled by thefollowing method. The length in the length direction of the portion ofthe external electrode located on the principal surface can becontrolled by, for example, varying the wettability to the conductivepaste on the ceramic body. The wettability to the conductive paste onthe ceramic body can be varied by, for example, applying a surfactant,or carrying out plasma treatment or the like.

In this regard, any of the following conditions (1) to (5) is preferablysatisfied in the multilayer ceramic capacitor 1.

Condition 1

The internal electrode located closest to the first principal surface ispreferably configured so that the multilayer ceramic capacitor 1 isabout 0.9 mm or more and about 1.1 mm or less in length dimension, themultilayer ceramic capacitor 1 is about 0.4 mm or more and about 0.6 mmor less in width dimension, the multilayer ceramic capacitor 1 is about0.085 mm or more and about 0.11 mm or less in height dimension, and theratio (T_(MAX)−T_(MIN))/T of about 1.0% to about 5.0% is met. The targetdimensions of the multilayer ceramic capacitor 1 preferably are about1.0 mm in length dimension, about 0.5 mm in width dimension, and about0.10 mm in height dimension.

Condition 2

The internal electrode located closest to the first principal surface ispreferably configured so that the multilayer ceramic capacitor is about0.9 mm or more and about 1.1 mm or less in length dimension, themultilayer ceramic capacitor is about 0.4 mm or more and about 0.6 mm orless in width dimension, the multilayer ceramic capacitor is about 0.12mm or more and about 0.15 mm or less in height dimension, and the ratio(T_(MAX)−T_(MIN))/T of about 1.3% to about 5.3% is met. The targetdimensions of the multilayer ceramic capacitor 1 preferably are about1.0 mm in length dimension, about 0.5 mm in width dimension, and about0.15 mm in height dimension.

Condition 3

The internal electrode located closest to the first principal surface ispreferably configured so that the multilayer ceramic capacitor is about0.9 mm or more and about 1.1 mm or less in length dimension, themultilayer ceramic capacitor is about 0.4 mm or more and about 0.6 mm orless in width dimension, the multilayer ceramic capacitor is about 0.18mm or more and about 0.20 mm or less in height dimension, and the ratio(T_(MAX)−T_(MIN))/T of about 1.5% to about 5.0% is met. The targetdimensions of the multilayer ceramic capacitor 1 preferably are about1.0 mm in length dimension, about 0.5 mm in width dimension, and about0.20 mm in height dimension.

Condition 4

The internal electrode located closest to the first principal surface ispreferably configured so that the multilayer ceramic capacitor is about0.9 mm or more and about 1.1 mm or less in length dimension, themultilayer ceramic capacitor is about 0.4 mm or more and about 0.6 mm orless in width dimension, the multilayer ceramic capacitor is about 0.21mm or more and about 0.23 mm or less in height dimension, and the ratio(T_(MAX)−T_(MIN))/T of about 1.8% to about 5.9% is met. The targetdimensions of the multilayer ceramic capacitor 1 preferably are about1.0 mm in length dimension, about 0.5 mm in width dimension, and about0.22 mm in height dimension.

Condition 5

The internal electrode located closest to the first principal surface ispreferably configured so that the multilayer ceramic capacitor is about0.9 mm or more and about 1.1 mm or less in length dimension, themultilayer ceramic capacitor is about 0.4 mm or more and about 0.6 mm orless in width dimension, the multilayer ceramic capacitor is about 0.24mm or more and about 0.30 mm or less in height dimension, and the ratio(T_(MAX)−T_(MIN))/T of about 1.2% to about 6.0% is met. The targetdimensions of the multilayer ceramic capacitor 1 preferably are about1.0 mm in length dimension, about 0.5 mm in width dimension, and about0.25 mm in height dimension.

The multilayer ceramic capacitor 1 preferably meets any of theconditions (1) to (5). For this reason, the ceramic body 10 isreinforced in a preferred manner with the first and second internalelectrodes 11, 12, and the stress applied to the ceramic body 10 whenthe multilayer ceramic capacitor 1 is mounted with the use of a mounteris effectively dispersed. Accordingly, the ceramic body 10 is moreunlikely to be cracked in mounting the multilayer ceramic capacitor 1.Because cracks are unlikely to be generated, the generation of shortcircuit defects in the multilayer ceramic capacitor 1 is effectivelysuppressed or prevented.

In firing the raw ceramic body with the conductive paste layers thatdefine the first and second base layers 13 a, 14 a, the conductive pastelayers contract more than the raw ceramic body. For this reason, tensilestress is applied to ridges of the ceramic body 10 by contraction ofportions of the conductive paste layers located on the principalsurfaces, and contraction of portions of the conductive paste layerslocated on the end surfaces. This tensile stress makes cracks likely tobe generated from the ridges of the ceramic body 10.

In this regard, as shown in FIG. 9, the height of an effective portion Ethat is a portion of the ceramic body 10 where the first and secondinternal electrodes 11, 12 are provided is referred to as A in theheight direction T. The height of a first outer layer portion that is aportion of the ceramic body 10 located closer to the first principalsurface 10 a than the effective portion E is referred to as B in theheight direction T. The height of a second outer layer portion that is aportion of the ceramic body 10 located closer to the second principalsurface 10 b than the effective portion E is referred to as C in theheight direction T.

In the multilayer ceramic capacitor 1, the ratios A/B and A/C eachpreferably falls within the range of about 0.5 to about 16. For thisreason, the crack generation in the ceramic body 10 that starts from thecontact point between the first principal surface 10 a of the ceramicbody 10 and the end of the external electrode is effectively suppressedor prevented. As the reason therefor, the following reason isconsidered. In the multilayer ceramic capacitor 1, the ratio of theheight of the first and second outer layer portions to the height of theeffective portion E is decreased when the ratios A/B and A/C are eachadjusted in the range of about 0.5 to about 16. More specifically, thefirst and second outer layer portions become relatively smaller inheight. For this reason, when the ceramic body 10 is subjected tofiring, compressive stress applied to the first and second outer layerportions is likely to be increased, due to contraction of the conductivepaste layers to define the internal electrodes. For this reason, forexample, in the case of baking the external electrodes 13, 14 afterfiring the ceramic body 10, the compressive stress of the first andsecond outer layer portions is able to be increased before baking theexternal electrodes 13, 14. For this reason, tensile stress is lesslikely to be applied to the ceramic body 10, even when the conductivepaste layers to define the external electrodes 13, 14 are contracted inbaking the external electrodes 13, 14. Therefore, the ceramic body 10 isbelieved to be less likely to be cracked. Even in the case ofsimultaneously carrying out firing for the ceramic body 10 and firing todefine the external electrodes 13, 14, tensile stress is less likely tobe applied to the ceramic body 10 for the same reason, and thus believedto be less likely to be applied to the ceramic body 10.

From the perspective of effectively suppressing or preventing crackgeneration in the ceramic body 10, when the dimension of the multilayerceramic capacitor 1 in the height direction T is about 50 μm to about150 μm, the ratios of A/B and A/C each preferably fall within the rangeof about 0.6 to about 6. When the dimension of the multilayer ceramiccapacitor 1 in the height direction T is about 150 μm to about 250 μm,the ratios of A/B and A/C each preferably fall within the range of about2 to about 16.

Multilayer ceramic capacitors preferably have external electrodes thatare unlikely to be peeled. In the multilayer ceramic capacitor 1, aboundary layer 20 containing about 5 atomic % to about 15 atomic % ofTi, about 5 atomic % to about 15 atomic % of Si, and about 2 atomic % toabout 10 atomic % of V (see FIG. 11) is preferably provided between theceramic body 10 and the base layers 13 a, 14 a. For this reason, theexternal electrodes 13, 14 are unlikely to be peeled in the case of themultilayer ceramic capacitor 1.

It is to be noted that as a cause of the fact that the externalelectrodes are unlikely to be peeled, for example, it is conceivablethat when the ceramic body with the base layers formed is immersed in aCu plating bath in order to form Cu plated layers, glass in the baselayers is eluted to decrease the adhesion strength between the baselayers and the ceramic body. Therefore, when the boundary layer 20containing about 5 atomic % to about 15 atomic % of Ti, about 5 atomic %to about 15 atomic % of Si, and about 2 atomic % to about 10 atomic % ofV is provided between the ceramic body 10 and the base layers 13 a, 14a, the boundary layer 20 which has this composition is formed in such away that a ceramic component of the ceramic body is reacted with a glasscomponent in the conductive paste layers in firing the ceramic body 10.The boundary layer 20 has excellent resistance to acids and alkalis, andhas low solubility in Cu plating baths such as a sulfuric acid Cu bath,a pyrophosphoric acid Cu bath, and a cyan Cu bath. For this reason, theadhesion strength between the base layers 13 a, 14 a and the ceramicbody 10 is unlikely to be decreased in the case of forming the Cu platedlayers 13 b, 14 b. Accordingly, the external electrodes 13, 14 arebelieved to be unlikely to be peeled on the ceramic body 10.

From the perspective of effective suppression or prevention of peelingof the external electrodes 13, 14, the maximum thickness of the boundarylayer 20 is preferably about 0.5 μm to about 5 μm. The externalelectrodes may be peeled from the ceramic body when the maximumthickness of the boundary layer 20 is smaller than about 0.5 μm, whereasthe deflective strength may be decreased because of a decrease in thestrength itself of the ceramic body when the maximum thickness of theboundary layer 20 is larger than about 5 μm. The glass included in theceramic body preferably includes at least one of B₂O₃ and SiO₂; and atleast one selected from the group consisting of Al₂O₃, ZnO, CuO, Li₂O,Na₂O, K₂O, MgO, CaO, BaO, ZrO₂, SrO, V₂O₅, and TiO₂.

Further, in the following description, t1 to t3 shown in FIG. 11 will bedefined as follows.

The maximum thickness of a portion of the first external electrode 13located on the first end surface 10 e is referred to as t1 in a crosssection passing through the center in the width direction W andextending in the length direction L and the height direction T.

The maximum thickness of a portion of the first external electrode 13located on the first principal surface 10 a is referred to as t2 in across section passing through the center in the width direction W andextending in the length direction L and the height direction T.

The thickness of the first external electrode 13 on a line passingthrough the point of intersection between a tangent line on a corner ofthe ceramic body 10 and the corner and the point of intersection betweena line along the first principal surface 10 a and a line along the firstend surface 10 e is referred to as t3 in a cross section passing throughthe center in the width direction W and extending in the lengthdirection L and the height direction T.

Now, the multilayer ceramic capacitor 1 is embedded into a multilayerprinted wiring board, and used. In such a case, the multilayer ceramiccapacitor 1 is required to have excellent resistance to moisture, andexcellent adhesion to the resin constituting the multilayer printedwiring board.

The inventor has, as a result of earnest study, conceived of therelationships between the shape of the external electrode, and themoisture resistance of the multilayer ceramic capacitor 1 and theadhesion to the resin. Specifically, the inventor has discovered thatthe relationships among t1 to t3 can control the moisture resistance andthe adhesion to the resin.

In the multilayer ceramic capacitor 1, the ratio t2/t1 is preferablyabout 0.7 to about 1.0, and the ratio t3/t1 is preferably about 0.4 toabout 1.2. In this case, a multilayer ceramic capacitor that hasexcellent resistance to moisture, and excellent adhesion to the resin ofthe multilayer printed wiring board is achieved.

An excessively small ratio t2/t1 may result in failure to efficientlyensure the thicknesses of the external electrodes 13, 14 around cornersof the ceramic body 10, and ingress of plating solutions, etc., into themultilayer ceramic capacitor 1, thus decreasing reliability ofresistance to moisture. An excessively large ratio t2/t1 may eliminatethe roundness of the external electrodes 13, 14 around corners of theceramic body 10, and make stress more likely to be concentrated on thecorners, thus decreasing the adhesion between the multilayer ceramiccapacitor 1 and the resin of the multilayer printed wiring board.

An excessively small ratio t3/t1 may result in failure to efficientlyensure the thicknesses of the external electrodes 13, 14, and ingress ofplating solutions, etc., into the multilayer ceramic capacitor 1, thusdecreasing the moisture resistance. An excessively large ratio t3/t1 mayeliminate the roundness of the external electrodes 13, 14 around cornersof the ceramic body 10, and make stress more likely to be concentratedon the corners, thus decreasing the adhesion between the multilayerceramic capacitor 1 and the resin of the multilayer printed wiringboard.

It is to be noted that t1 to t3 can be measured in the following manner.

Method of t1 Measurement

A cross section is exposed by polishing the first or second side surface10 c, 10 d of the multilayer ceramic capacitor 1 until the height of themultilayer ceramic capacitor 1 in the width direction W is reduced downto about ½. The maximum thickness t1 of the portion of the firstexternal electrode 13 located on the first end surface 10 e can bemeasured by observing the cross section with the use of a microscope.

Method of t2 Measurement

A cross section is exposed by polishing the first or second side surface10 c, 10 d of the multilayer ceramic capacitor 1 until the height of themultilayer ceramic capacitor 1 in the width direction W is reduced downto about ½. The maximum thickness t2 of the portion of the firstexternal electrode 13 located on the first principal surface 10 a can bemeasured by observing the cross section with the use of a microscope.

Method of t3 Measurement

A cross section is exposed by polishing the first or second side surface10 c, 10 d of the multilayer ceramic capacitor 1 until the height of themultilayer ceramic capacitor 1 in the width direction W is reduced downto about ½. The thickness t3 of the first external electrode 13 on theline passing through the point of intersection between the tangent lineon the corner of the ceramic body 10 and the corner and the point ofintersection between the line along the first principal surface 10 a andthe line along the first end surface 10 e can be measured by observingthe cross section with the use of a microscope.

It is to be noted that the arithmetic mean roughness (Ra) at thesurfaces of the external electrodes 13, 14 is preferably larger than thearithmetic mean roughness (Ra) at the surface of the ceramic body 10 inthe present preferred embodiment. More specifically, the ratio of (thearithmetic mean roughness (Ra) at the surface of the ceramic body10)/(the arithmetic mean roughness (Ra) at the surfaces of the externalelectrodes 13, 14) preferably falls within the range of about 0.06 ormore and about 0.97 or less. In the calculation of the arithmetic meanroughness (Ra) at the surface of the ceramic body 10, as a measurementcondition, a laser microscope (Product Name: VK-9510) from KeyenceCorporation is preferably used at a 100-fold lens magnification in acolor ultradeep mode set. The range of measurement with the lasermicroscope is regarded as a region of about 90 μm square including acentral portion of the principal surface 10 a of the ceramic body 10.Then, the arithmetic mean roughness (Ra) at the surface of the ceramicbody 10 is regarded as a value calculated on the basis of the surfaceroughness measured under the measurement condition.

On the other hand, in the calculation of the arithmetic mean roughness(Ra) at the surfaces of the external electrodes 13, 14, as a measurementcondition, a laser microscope (Product Name: VK-9510) from KeyenceCorporation is preferably used at a 100-fold lens magnification in acolor ultradeep mode set. The range of measurement with the lasermicroscope is regarded as a region of about 90 μm square including acentral portion of a portion of the external electrode 13 or externalelectrode 14 provided on the principal surface 10 a or the principalsurface 10 b. Then, the arithmetic mean roughness (Ra) at the surfacesof the external electrodes 13, 14 is regarded as a value calculated onthe basis of the surface roughness measured under the measurementcondition.

As described above, the arithmetic mean roughness (Ra) at the surfacesof the external electrodes 13, 14 is preferably larger than thearithmetic mean roughness (Ra) at the surface of the ceramic body. Morespecifically, the ratio of (the arithmetic mean roughness (Ra) at thesurface of the ceramic body 10)/(the arithmetic mean roughness (Ra) atthe surfaces of the external electrodes 13, 14) preferably falls withinthe range of about 0.06 or more and about 0.97 or less. For this reason,in the case of closely contacting the resin of the multilayer printedwiring board with the multilayer ceramic capacitor 1 in embedding themultilayer ceramic capacitor 1 into the multilayer printed wiring board,the close contact between the external electrodes 13, 14 and the resinin an embedding concave portion for the capacitor, which is provided inthe multilayer printed wiring board, is made stronger than the closecontact between the ceramic body 10 and the resin in an embeddingconcave portion for the capacitor, which is provided in the multilayerprinted wiring board. Therefore, gaps are more unlikely to be producedbetween the external electrodes 13, 14 and the resin in the embeddingconcave portion for the capacitor, which is provided in the multilayerprinted wiring board. Accordingly, ingress of moisture into the gaps isalso suppressed or prevented. As a result, reliability of resistance tomoisture is ensured for the multilayer ceramic capacitor 1.

Further, methods to achieve the configuration as described aboveinclude, for example, the following method. The ceramic body 10 withdesired arithmetic mean roughness (Ra) can be created by providing thesurface of a mold for use in pressing with appropriate surfaceroughness, if necessary, in the step of pressing the mother laminatebody. It is to be noted that methods to adjust the arithmetic meanroughness (Ra) at the surface of the ceramic body 10 to desiredarithmetic mean roughness (Ra) include a method of applying a physicalimpact (for example, polishing) to the surface of the ceramic body 10,and a chemical treatment method (for example acid etching).

As shown in FIG. 4, the first external electrode 13 of the multilayerceramic capacitor 1 is preferably configured so that when the distancefrom the position of the maximum thickness on the principal surface 10 aof the ceramic body 10 to the position of the maximum thickness on theend surface 10 e of the ceramic body 10 is referred to as a dimension E(hereinafter, which may be referred to as an “E dimension”), whereas thedistance from the position of the maximum thickness on the end surface10 e of the ceramic body 10 to an edge end of the external electrode 13on the principal surface 10 a of the ceramic body 10 is referred to as adimension e (hereinafter, which may be referred to as an “e dimension”),the ratio E/e is about 0.243 or more and about 0.757 or less.

The dimension E and the dimension e are measured by polishing, for across section, the side surface of the multilayer ceramic capacitor 1 inthe length direction L until reaching about ½ the dimension in the widthdirection, and observing the polished surface with an opticalmicroscope. Specifically, the dimensions are measured by the followingmethods.

(1) Method of E Dimension Measurement

In order to measure the E dimension, the side surface of the multilayerceramic capacitor 1 is polished in the length direction L until thedimension in the width direction W is reduced down to about ½, and thepolished surface is subjected to measurement with an optical microscope.Specifically, in regard to portions located on the principal surface 10a, 10 b, of the external electrodes 13, 14 provided on the principalsurface 10 a or principal surface 10 b of the ceramic body 10, thedistances are measured from the position of the maximum thickness in theheight direction T for each of the portions located on the principalsurface 10 a, 10 b, to the position of the maximum thickness in thelength direction L for the external electrode 13, 14 provided on the endsurface 10 e or end surface 10 f of the ceramic body 10. Then, theaverage for the respective measurement values is regarded as the Edimension.

(2) Method of e Dimension Measurement

In order to measure the e dimension, the side surface of the multilayerceramic capacitor 1 is polished in the length direction L until thedimension in the width direction W is reduced down to about ½, and thepolished surface is subjected to measurement with an optical microscope.Specifically, the distances are measured from the position of themaximum thickness in the length direction L for the external electrode13, 14 formed on the end surface 10 e or end surface 10 f of the ceramicbody 10, to edge ends of portions located on the principal surface 10 a,10 b, of the external electrodes 13, 14 provided on the principalsurface 10 a or principal surface 10 b of the ceramic body 10. Then, theaverage for the respective measurement values is regarded as the edimension.

As just described, the formation is preferably achieved so that theratio E/e is about 0.243 or more and about 0.757 or less. Thus, thestress concentration generated at corners of the multilayer ceramiccapacitor 1 is significantly reduced or prevented. As a result, itbecomes possible to suppress or prevent peeling that is generatedbetween the corners of the multilayer ceramic capacitor 1 and the resinin the embedding concave portion for the capacitor, which is provided inthe multilayer printed wiring board.

Further, methods for making an adjustment so that the ratio E/e is about0.243 or more and about 0.757 or less include, for example, thefollowing method. The ratio E/e can be adjusted by adjusting therheology of the conductive paste to define the first and second baselayers 13 a, 14 a, applying surface treatment to the ceramic body 10, orapplying the conductive paste more than once.

As shown in FIG. 5, when the maximum thickness and average thickness ofa portion of the first external electrode 13 located on the principalsurfaces 10 a, 10 b of the ceramic body 10 are denoted respectively byD_(max) and D_(ave), the condition expression ofD_(ave)×250%≧D_(max)≧D_(ave)×120% is preferably satisfied.

Likewise, when the maximum thickness and average thickness of a portionof the second external electrode 14 located on the principal surfaces 10a, 10 b of the ceramic body 10 are denoted respectively by Dmax andDave, the condition expression of D_(ave)×250%≦D_(max)≦D_(ave)×120% ispreferably satisfied.

It is to be noted that the maximum thickness D_(max) and the averagethickness D_(ave) are measured by polishing the side surface of themultilayer ceramic capacitor 1 in the length direction L until thedimension in the width direction W is reduced down to about ½, andobserving the polished surface with an optical microscope. Specifically,the thicknesses are measured by the following methods.

(1) Method of D_(max) Measurement

In order to measure the maximum thickness D_(max), the side surface ofthe multilayer ceramic capacitor 1 is polished in the length direction Luntil the dimension in the width direction W is reduced down to about ½,and the polished surface is subjected to measurement with an opticalmicroscope. Specifically, the thicknesses of the thickest portions inthe height direction T for each of portions of the external electrodes13, 14 located on the principal surface 10 a or the principal surface 10b are measured for the measurement of the maximum thickness D_(max).Then, the average for the measurement values is regarded as the maximumthickness D_(max).

(2) Method of D_(ave) Measurement

In order to measure the average thickness D_(ave), the side surface ofthe multilayer ceramic capacitor 1 is polished in the length direction Luntil reaching about ½ the dimension in the width direction W, and thepolished surface is subjected to measurement with an optical microscope.Specifically, the thicknesses in the height direction T for ten equalportions obtained by dividing, in the length direction L, each of theportions of the external electrodes 13, 14 located on the principalsurface 10 a or the principal surface 10 b are measured for themeasurement of the average thickness D_(ave). Then, the average for themeasurement values is regarded as D_(ave).

When the condition expression of D_(ave)×250%≧D_(max)≧D_(ave)×120% issatisfied, the portions of the external electrodes 13, 14 located on theprincipal surfaces 10 a, 10 b are increased in thickness, and theportions of the external electrodes 13, 14 located on the principalsurfaces 10 a, 10 b function as cushioning materials, and disperse themounting load (stress) applied to the multilayer ceramic capacitor 1 insuctioning the multilayer ceramic capacitor 1 with a suction nozzle of amounting machine (mounter) or pushing the capacitor into a multilayerprinted wiring board. As a result, the generation of breakages andcracks is significantly reduced or prevented without concentrating themounting load (stress) on portions of the multilayer ceramic capacitor 1with mechanical strength decreased.

It is to be noted that the maximum thickness D_(max) and the averagethickness D_(ave) can be controlled by adjusting the pull-up rate afterdipping the ceramic body 10 in the conductive paste. The pull-up rateafter dipping the ceramic body 10 in the conductive paste can beadjusted to, for example, about 20 mm/min or more and about 1000 mm/minor less. The viscosity of the conductive paste is preferably about 10Pa·s or more and about 100 Pa·s or less.

As shown in FIG. 6, in the multilayer ceramic capacitor 1, the platedlayers 13 b, 14 b each preferably include a laminate body of two layersof Cu plated films. In this case, ingress of the Cu metal of each Cuplated film constituting the laminate body may be caused into the baselayer 13 a, 14 a, from the surface layer of the base layer 13 a, 14 aeven to the position of about ⅓ or more the thickness of the base layer13 a, 14 a. It is to be noted that in regard to the ingress of the metalof the plated film into the base layer 13 a, 14 a, when the side surface(surface LT) of the multilayer ceramic capacitor 1 is polished in thelength direction L to about ½ the dimension in the width direction W,and when a line is drawn along a portion of about ⅓ in height from thesurface layer of the base layer 13 a, 14 a in any observation visualview of about 30 μm in x-axis and about 30 μm in y-axis at the polishedsurface, including the base layer 13 a, 14 a provided on the principalsurface of the ceramic body, the metal of the plated film is preferablypresent at about 30% or more with respect to the total proportion of themetal of the base layer 13 a, 14 a and plated film on the line.

Each Cu plated film is preferably formed with the use of apyrophosphoric acid Cu plating solution or a cyanide Cu platingsolution. These plating solutions with high glass erosion capability,efficiently dissolve the glass contained in the base layer 13 a, 14 a,thus making ingress of the Cu metal of the Cu plated film likely to becaused into the base layer 13 a, 14 a. For this reason, the content rateof Cu is likely to be high in the base layers 13 a, 14 a.

The glass contained in the base layers 13 a, 14 a preferably containsBaO in an amount of about 10 weight % or more and about 50 weight % orless, SrO in an amount of about 10 weight % or more and about 50 weight% or less, B₂O₃ in an amount of about 3 weight % or more and about 30weight % or less, and SiO₂ in an amount of about 3 weight % or more andabout 30 weight % or less. In this case, the glass contained in the baselayers 13 a, 14 a is more easily dissolved in pyrophosphoric acid Cuplating solutions and cyanide Cu plating solutions.

It is to be noted that whether the ingress of the Cu metal of the Cuplated film into the base layers 13 a, 14 a is caused or not can beconfirmed by polishing the side surface of the multilayer ceramiccapacitor 1 in the length direction L until the dimension in the widthdirection W is reduced down to about ½, and observing the polishedsurface with an optical microscope. Specifically, the portion of theexternal electrode 13 located over the first principal surface 10 a isdetermined as “yes” in the case of ingress of the metal of the Cu platedfilm into the base layer 13 a from the surface layer of the base layer13 a even to the position of about ⅓ or more the thickness of the baselayer 13 a, or determined as “no” in the case of no ingress from thesurface layer of the base layer 13 a to the position of about ⅓ or morethe thickness of the base layer 13 a.

Furthermore, the metal thicknesses of the external electrodes 13, 14 arepreferably about 8.7 μm or more and about 13.9 μm or less. The metalthickness refers to a value obtained by measuring the thickness of themetal with a fluorescent X-ray film thickness meter (SFT-9400 from SeikoInstruments Inc.), and converting the measured X-ray Cu amount into afilm thickness. In regard to the measurement point, for example, in thecenter in planar view of the portion of the external electrode 13located over the first principal surface 10 a, the measurement can bemade.

The pyrophosphoric acid Cu plating solution and the cyanide Cu platingsolution have high glass erosion capability, and efficiently dissolvethe glass contained in the base layers 13 a, 14 a. For this reason, theuse of the pyrophosphoric acid Cu plating solution or cyanide Cu platingsolution easily causes ingress of the Cu metal of the Cu plated filminto the base layer 13 a, 14 a. Therefore, the content rate of Cu in thebase layers 13 a, 14 a is improved.

In the case of the formation that causes ingress of the Cu metal of theCu plated film into the base layer 13 a, 14 a from the surface layer ofthe base layer 13 a, 14 a to the position of about ⅓ or more thethickness of the base layer 13 a, 14 a, the Cu content rate is high inthe base layers 13 a, 14 a. Accordingly, in combination with the baselayers 13 a, 14 a and Cu plated films in total, the content rate of Cuper unit thickness is increased to improve the thermal conductivity(heat release performance) of the base layers 13 a, 14 a, and increasethe laser resistance of the external electrodes 13, 14.

Furthermore, in the case of the formation that causes ingress of the Cumetal of the Cu plated film into the base layer 13 a, 14 a from thesurface layer of the base layer 13 a, 14 a to the position of about ⅓ ormore the thickness of the base layer 13 a, 14 a, the difference in levelbetween the surface of the multilayer printed wiring board and thesurfaces of the external electrodes 13, 14 are reduced because theexternal electrodes 13, 14 are reduced in thickness. As a result, thegap between the surface of the multilayer printed wiring board and themounting surface of the ceramic body 10 is narrowed to make peeling lesslikely to be caused between the multilayer printed wiring board and theexternal electrodes 13, 14, and also improve the mechanical strength ofthe component.

Experimental Examples

Two hundred non-limiting examples of multilayer ceramic capacitors(target dimensions: about 1.0 mm in length dimension, about 0.5 mm inwidth dimension, about 0.15 mm in height dimension) configured insubstantially the same fashion as the multilayer ceramic capacitor 1were prepared for each example with the conditions shown in Table 1 inaccordance with the manufacturing method described above. It is to benoted that the respective samples were prepared by varying only c, d,and e, and keeping the other conditions substantially the same.

One hundred samples were mounted on a glass epoxy substrate with the useof a mounting machine to prepare a mounted product. It is to be notedthat the amounts of pushing the samples were adjusted to about 1.0 mm.Cross sections of the multilayer ceramic capacitors were exposed bypolishing, in the length direction, a cross section in the lengthdirection and height direction of the mounted product prepared until thedimensions in the width direction were reduced to about ½. The crosssections were observed with the use of a microscope to confirm thepresence or absence of a crack. The results are shown in Table 1.

Furthermore, the remaining one hundred samples prepared were mountedonto a glass epoxy substrate with the use of a conductive adhesive.Thereafter, a voltage of about 2 V was applied for about 72 hours to therespective samples disposed in a high-temperature and high-humidity tankat about 125° C. and about 95% relative humidity to carry out a humidityresistance acceleration test. Then, the samples with a two-digitdecrease in insulation resistance value (IR) were determined as sampleswith humidity resistance degraded.

TABLE 1 Experimental Example 1 2 3 4 5 6 a (μm) 20 20 20 20 20 20 b (μm)75 75 75 75 75 75 c (μm) 5 10 15 15 20 25 d (μm) 250 250 300 350 350 400e (μm) 5 10 15 15 20 25 f (μm) 100 100 100 100 100 100 (c · d + e ·f/2)/(a · b) 1 2 3.5 4 6 7.5 The Number of  0/100 0/100 0/100 0/1008/100 Samples Cracked/ Total Number of Samples The Number of 17/1000/100 0/100 0/100 0/100 0/100 Samples with Humidity Resistance Degraded/Total Number of Samples

While preferred embodiments of the present invention have been describedabove, it is to be understood that variations and modifications will beapparent to those skilled in the art without departing from the scopeand spirit of the present invention. The scope of the present invention,therefore, is to be determined solely by the following claims.

What is claimed is:
 1. A multilayer ceramic capacitor comprising: aceramic body including first and second principal surfaces extending ina length direction and a width direction, first and second side surfacesextending in the length direction and a height direction, and first andsecond end surfaces extending in the width direction and the heightdirection; a first internal electrode extending in the length directionand the width direction, provided in the ceramic body, and exposed atthe first end surface; a second internal electrode extending in thelength direction and the width direction, provided in the ceramic body,exposed at the second end surface, and the second internal electrodefacing the first internal electrode in the height direction with aceramic portion interposed therebetween; a first external electrodeconnected to the first internal electrode and provided over the firstend surface and over the first principal surface; a maximum thicknessand an average thickness of a portion of the first external electrodelocated on the first principal surface are denoted respectively byD_(max) and D_(ave); and D_(ave)×250%≧D_(max)≧D_(ave)×120% is satisfied.2. The multilayer ceramic capacitor according to claim 1, furthercomprising: a second external electrode connected to the second internalelectrode and provided over the second end surface and over a portion ofeach of the first and second principal surfaces; wherein the firstexternal electrode includes a first base layer provided over a portionof the ceramic body and including a metal and glass, and a first platedlayer provided over the first base layer; the second external electrodeincludes a second base layer provided over a portion of the ceramic bodyand including a metal and glass, and a second plated layer provided overthe second base layer; the first and second plated layers each include aCu plated layer.
 3. The multilayer ceramic capacitor according to claim1, wherein the multilayer ceramic capacitor is about 0.9 mm to about 1.1mm in length dimension, about 0.4 mm to about 0.6 mm in width dimension,and about 0.085 mm to about 0.15 mm in height dimension.
 4. Themultilayer ceramic capacitor according to claim 1, wherein a height ofan effective portion that is a portion of the ceramic body where thefirst and second internal electrodes overlap each other in the heightdirection is referred to as A in the height direction; and a height of afirst outer layer portion that is a portion of the ceramic body locatedbetween the first principal surface and the effective portion isreferred to as B in the height direction; and a height of a second outerlayer portion that is a portion of the ceramic body located between thesecond principal surface and the effective portion is referred to as Cin the height direction; each of ratios A/B and A/C is within a range ofabout 0.5 to about
 16. 5. The multilayer ceramic capacitor according toclaim 1, wherein the multilayer ceramic capacitor is about 0.9 mm ormore and about 1.1 mm or less in length dimension, about 0.4 mm or moreand about 0.6 mm or less in width dimension, and about 0.085 mm or moreand about 0.11 mm or less in height dimension, a maximum distance fromthe first principal surface to an internal electrode closest to thefirst principal surface among the first internal electrode and thesecond internal electrode in the height direction is referred to asT_(MAX); and a minimum distance from the first principal surface to theinternal electrode closest to the first principal surface in the heightdirection is referred to as T_(MIN); and a ratio (T_(MAX)−T_(MIN))/T isabout 1.0% to about 5.0%.
 6. The multilayer ceramic capacitor accordingto claim 1, wherein the multilayer ceramic capacitor is about 0.9 mm ormore and about 1.1 mm or less in length dimension, about 0.4 mm or moreand about 0.6 mm or less in width dimension, and about 0.12 mm or moreand about 0.15 mm or less in height dimension; a maximum distance fromthe first principal surface to an internal electrode closest to thefirst principal surface among the first internal electrode and thesecond internal electrode in the height direction is referred to asT_(MAX); and a minimum distance from the first principal surface to theinternal electrode closest to the first principal surface in the heightdirection is referred to as T_(MIN); and a ratio (T_(MAX)−T_(MIN))/T isabout 1.3% to about 5.3%.
 7. The multilayer ceramic capacitor accordingto claim 1, wherein the multilayer ceramic capacitor is about 0.9 mm ormore and about 1.1 mm or less in length dimension, about 0.4 mm or moreand about 0.6 mm or less in width dimension, and about 0.18 mm or moreand about 0.20 mm or less in height dimension; a maximum distance fromthe first principal surface to an internal electrode closest to thefirst principal surface among the first internal electrode and thesecond internal electrode in the height direction is referred to asT_(MAX); and a minimum distance from the first principal surface to theinternal electrode closest to the first principal surface in the heightdirection is referred to as T_(MIN); and a ratio (T_(MAX)−T_(MIN))/T isabout 1.5% to about 5.0%.
 8. The multilayer ceramic capacitor accordingto claim 1, wherein the multilayer ceramic capacitor is about 0.9 mm ormore and about 1.1 mm or less in length dimension, about 0.4 mm or moreand about 0.6 mm or less in width dimension, and about 0.21 mm or moreand about 0.23 mm or less in height dimension; a maximum distance fromthe first principal surface to an internal electrode closest to thefirst principal surface among the first internal electrode and thesecond internal electrode in the height direction is referred to asT_(MAX); a minimum distance from the first principal surface to theinternal electrode closest to the first principal surface in the heightdirection is referred to as T_(MIN); and a ratio (T_(MAX)−T_(MIN))/T isabout 1.8% to about 5.9%.
 9. The multilayer ceramic capacitor accordingto claim 1, wherein the multilayer ceramic capacitor is about 0.9 mm ormore and about 1.1 mm or less in length dimension, about 0.4 mm or moreand about 0.6 mm or less in width dimension, and about 0.024 mm or moreand about 0.30 mm or less in height dimension; a maximum distance fromthe first principal surface to an internal electrode closest to thefirst principal surface among the first internal electrode and thesecond internal electrode in the height direction is referred to asT_(MAX); a minimum distance from the first principal surface to theinternal electrode closest to the first principal surface in the heightdirection is referred to as T_(MIN); and a ratio (T_(MAX)−T_(MIN))/T isabout 1.2% to about 6.0%.
 10. The multilayer ceramic capacitor accordingto claim 1, wherein a distance in the length direction from a positionof a surface at a maximum dimension in the height direction of the firstexternal electrode on the first principal surface to a position of asurface at a maximum dimension of the first external electrode in thelength direction on the first end surface is referred to as E; and adistance in the length direction from the position of the surface at themaximum dimension on the first end surface to an edge end of the firstexternal electrode on the first principal surface is referred to as e; aratio E/e is about 0.243 or more and about 0.757 or less.
 11. Themultilayer ceramic capacitor according to claim 1, wherein a heightdimension of the ceramic body is DT, a length dimension of the ceramicbody is DL, and a width dimension of the ceramic body is DW, and arelationship ( 1/7)DW≦DT≦(¼)DW is satisfied.
 12. The multilayer ceramiccapacitor according to claim 1, wherein a height dimension of theceramic body is DT and a relationship DT<about 0.15 mm is satisfied. 13.The multilayer ceramic capacitor according to claim 1, wherein theceramic portion is about 0.5 μm to about 10 μm in height.
 14. Themultilayer ceramic capacitor according to claim 1, wherein each of thefirst internal electrode and the second internal electrode is about 0.2μm to about 2 μm in height.
 15. The multilayer ceramic capacitoraccording to claim 2, wherein each of the first and second base layersis about 1 μm to about 20 μm in thickness.
 16. The multilayer ceramiccapacitor according to claim 2, wherein the Cu plated layer is about 1μm to about 10 μm in thickness.
 17. The multilayer ceramic capacitoraccording to claim 2, wherein the Cu plated layer includes a pluralityof plated films.
 18. An electronic component comprising: a multilayerprinted wiring board; and the multilayer ceramic capacitor according toclaim 1 embedded in the multilayer printed wiring board.
 19. Theelectronic component according to claim 18, wherein a via hole isprovided in the multilayer printed wiring board to provide electricalconnection to the multilayer ceramic capacitor.